Bug Description

Brightness doesn't work using acpi from video driver with default kernel option "acpi_backlight=video"

Using kernel option "acpi_backlight=vendor" this allow vendor acpi driver to control brightness hotkeys.
reported to work with Dell Mini and Asus EEEPC (eeepc-wmi and dell_backlight modules) but this doens't work with acer-wmi.
"ls /sys/class/backlight" shows these modules.

Swithching off "acpi=off" fixes brightness issue but it is not recommended to disable acpi.

The strange thing is that kernel 2.6.38 has a stub gpu module (called poulsbo) that should call "acpi_video_register()" and fix
"acpi_backlight=video" for all vendors.. but unfortunately doesn't seem to work.

"Currently, there have no GMA500(Poulsbo) native video driver to support
intel opregion. So, use this stub driver to enable the acpi backlight
control sysfs entry files by requrest acpi_video_register."